1. Field of the Invention
This invention relates to electric discharge lamps and has particular reference to a compact fluorescent lamp unit adapted for use as a direct replacement for incandescent lamps in fixtures employed for residential and commercial lighting purposes.
2. Description of the Prior Art
Fluorescent lamp units having integral circuit and base components which permit the lamp unit to be screwed into and operated in a socket of a fixture that is designed for incandescent lamps are generally well-known in the art. An electrodeless fluorescent lamp assembly of this type that is energized by a high frequency voltage produced by a self-contained radio-frequency oscillator is disclosed in U.S. Pat. No. 3,521,120 granted July 21, 1970 to J. M. Anderson. Another fluorescent lamp unit which is designed for use in conventional light fixtures and has an envelope that contains concentric annular partitions and electrodes and is coupled to a screw-type base and a ballast component, starter and condenser which permit the lamp to be operated on an AC power supply is disclosed in U.S. Pat. No. 3,551,736 granted Dec. 29, 1970 to G. A. Doehner.
Fluorescent lamps that are designed for direct-current operation and have integral means for counteracting the cataphoretic "pumping" effect which causes the mercury vapor within the operating lamp to accumulate in the region around the cathode are also known in the art. A panel-shaped discharge lamp having partition members that are composed of porous ceramic or vitreous material (or which are provided with inserts of such material) that permit the mercury vapor to circulate within the envelope and between the partitions when the lamp is being operated on a DC power source is disclosed in U.S. Pat. No. 3,258,630 granted June 28, 1966 to W. J. Scott.
A gaseous discharge lamp unit of rectangular configuration in which two sections of straight glass tubing are joined together by U-shaped end members to form an envelope which contains a diaphragm that separates the electrodes but is permeable to mercury vapor and thus prevents the cataphoretic pumping of mercury vapor during DC operation is disclosed in German Patent Application No. 2,549,419 of A. Walz filed Nov. 4, 1975 and opened to inspection May 5, 1977.
Other types of fluorescent lamps that have partitioned envelopes or are provided with fillers or end plugs of glass wool or metal wool for various purposes are described in the following U.S. Pat. Nos.: U.S. Pat. No. 2,121,333 granted June 21, 1938 to Barclay, U.S. Pat. No. 3,024,383 granted Mar. 6, 1962 to Doering, U.S. Pat. No. Re. 22,896 granted July 8, 1947 to Polevitzky, U.S. Pat. No. 3,508,103 granted Apr. 21, 1970 to Young, U.S. Pat. No. 3,609,436 granted Sept. 28, 1971 to Campbell, U.S. Pat. No. 2,133,205 granted Oct. 11, 1938 to McCauley, and, U.S. Pat. No. 2,824,993 granted Feb. 25, 1958 to DeVriend et al.